The present invention relates to a motor-vehicle door latch. More particularly this invention concerns such a latch provided with a power closer.
A motor-vehicle door latch, for instance used on a side door of the pivoting or sliding type, on a sliding sun roof, or even on a pivoting trunk lid is often provided with a power closer that itself effects the final closing movement of the door. Thus the user typically pushes the door into an intermediate position in which the door is slightly ajar and in which elements of the latch and the door interengage, and thereafter the power closer pulls the door into an end position flush with the vehicle. The door latch typically comprises a pivotal fork mounted on the door post or door edge, and a bolt fittable in the fork and mounted on the door edge or post. The power closer can be connected to the fork or to the bolt so as to effect the movement from the intermediate partially closed position to the end fully closed position.
In order to prevent the door from closing on a finger and to avoid damage to the door and/or the power closer, it is standard to provide a system that will stop the power closing when certain conditions are present. In the simplest system the force, typically a torque, exerted by the actuator, normally a rotary electric motor, is monitored and when it exceeds a predetermined limit the power closing is stopped and, often, the door movement is even reversed. Such crude systems are only barely effective and often can exert enough force to, for instance, pinch a person badly enough to cause a serious injury. If they are set to be too sensitive, the door does not close just when a sticky part of the track or something is encountered.
Accordingly U.S. Pat. No. 4,585,981 proposes a system that uses a potentiometer as described in U.S. Pat. No. 4,556,835 to detect the actual position of the door. This actual-position signal is monitored with respect to time to produce a speed signal that in turn is differentiated to produce an output corresponding to acceleration or deceleration. When the door decelerates too much, indicating something is in its path, the closing movement is stopped and even reversed. Such an arrangement has the disadvantage that a standard door, for instance a sun roof, is likely to move at substantially different speeds as it travels from a fully open to a fully closed position even when operating perfectly with nothing in the way. Thus the threshold has to be set fairly high to correspond, for instance, to the rapid deceleration as the door comes into contact with a seal. Thus if something can be pinched rather forcefully in the door before it stops and reverses.
In U.S. Pat. No. 6,176,528 another arrangement is described which ascertains several exact positions of the door. This system is used typically with a trunk lid to prevent it from automatically closing again if its latch is released when there is some weight, for instance ice, on it preventing it from popping open. Thus the system does not allow the power-closing action to take place until the door has moved outward past a predetermined intermediate position. As a result if some weight holds the door down when its latch is released, the user can still force it open and subsequently close it with the standard power-closing feature.
Another system described in European 0,979,915 proposes a latch for a motor-vehicle door. On actuation of an unlocking mechanism there is simultaneously a mechanical interruption of the force applied between the drive of the power closer and the closing door. Another latch described in German 199 28 509 is provided with a system for monitoring the instantaneous position of the door, much as in above-cited U.S. Pat. No. 4,556,835. This system serves for trunk lids or doors of a motor vehicle with a closing element and two read/writable memories in which are stored desired positions the door should reach. The system compares the actual position of the door with the desired position to control opening and/or closing of the door. Such a system is relatively complex and does not, once again, take into account the different resistances to movement and speed profile of the door as it moves between open and closed end positions.
It is therefore an object of the present invention to provide an improved power-closing door latch for a motor vehicle.
Another object is the provision of such an improved power-closing door latch for a motor vehicle which overcomes the above-given disadvantages, that is which prevents the power closer from operating in a manner tailored to the particular characteristics of movement of the door.
A motor-vehicle door latch has according to the invention a pair of engageable parts one of which is movable between a pair of end positions and through an intermediate position between the end positions and a pair of end-position sensors and an intermediate position sensor operable when the parts reach the respective positions for generating respective outputs. A drive engages at least one of the parts for displacing the parts from one end position through the intermediate position into the other end position. A controller connected to the drive and to the sensors operates the drive to displace the parts from the one end position to the intermediate position only when travel of the parts from the one end position to the intermediate position takes place in less than a predetermined first time and displaces the parts from the intermediate position to the other end position only when travel of the parts from the intermediate position to the other end position takes place in less than a predetermined second time different from the first time.
Thus with this system it is possible to set different response characteristics for the latch for different parts of its closing movement. It can be made relatively sensitive to blockages during the initial stages of its closing, but less sensitive in the later stages when it must compress the door seal, for instance.
The controller according to the invention reverses the drive when travel of the parts from the one end position to the intermediate position exceeds the first time and when travel of the parts from the intermediate position to the other end position exceeds the second time. Thus if something blocks the door, it will open again.
The one end position corresponds to a partially latched position of the latch in accordance with the invention. The intermediate position corresponds to a latched position of the latch. The other end position corresponds to an overtravel position of the latch, past the latched position.
The one part is a pivotal fork and the other part is a bolt engageable therewith. The drive includes a motor having a rotary output, a wheel carried on the output, a link connected between the wheel and the fork for pivoting of the fork on rotation of the wheel. The fork is pivotal about an axis and two of the sensors are axially spaced from one another but angularly aligned. The fork having a pair of axially spaced arms of angularly different lengths engageable with the two sensors.